TK 61555-2-MM-EN
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1.
Attach a clamp-on ammeter to the 2A wire near the B+ terminal on the alternator.
2.
Energize the field on the Thermo King alternator by connecting a jumper wire between the F2
terminal and the B+ terminal. Do not connect the F2 terminal to ground or the alternator will
be damaged.
3.
Note the ammeter reading. The ammeter reading indicates the field current, which should be
2.0 to 6.0 amps at 12 volts.
a.
No field current or a low field current indicates an open circuit or excessive resistance in
the field circuit. Remove the voltage regulator and brush assembly and inspect the slip
rings. If the slip rings and are acceptable, install a new voltage regulator and brush
assembly and repeat the test. If the brushes are not the problem, replace the alternator.
b.
High field current indicates a short in the field circuit. Replace the rotor or the alternator.
Battery
Filler Cap Batteries
1.
Inspect/clean the battery terminals and check the electrolyte level during scheduled
maintenance inspections.
2.
A dead or low battery can be the cause of an ammeter indicating discharge due to lack of
initial excitation of the alternator even after the unit has been boosted for starting.
3.
The minimum specific gravity should be 1.235.
4.
Add distilled water as necessary to maintain the proper water level.
Maintenance Free Batteries
1.
Inspect/clean the battery terminals and check the electrolyte level using the integrated sight
glass during scheduled maintenance inspections.
2.
A dead or low battery can be the cause of an ammeter indicating discharge due to lack of
initial excitation of the alternator even after the unit has been boosted for starting.
Battery Load Test
1. Verify battery voltage of at least 12.5v before load testing.
2. Apply 50% Cold Cranking Amps (CCA) load for 15 seconds and verify minimum voltage of
9.6v.
Battery Cables
The units use 0-gauge battery cables to ensure reliable starting in extremely cold weather. Verify
the use of the 0-gauge battery cables when replacing the battery cables. Refer to the unit Parts
Manual for the correct part numbers.
